Here's what you need

Check that your iOS device, Apple Watch, or HomePod is connected to a Wi-Fi or cellular network.

To use “Hey Siri” to control your HomeKit accessories hands-free, you need an iPhone or iPad* with the latest version of iOS, Apple Watch with the latest version of watchOS, or HomePod. You can also use Siri on Apple TV 4K or Apple TV (4th generation) to control your home by holding down the Siri button on your Siri Remote.

To control your HomeKit accessories remotely with Siri, you need to set up a home hub.